1. Field of the Invention
The present invention relates to a plate conveyance apparatus and a plate processing system using such plate conveyance apparatus, which are capable of loading an unprocessed plate material or sheet metal onto a plate processing machine and unloading a processed plate material from such plate processing machine.
2. Description of the Related Art
The plate material conveyance apparatus capable of loading unprocessed plate materials onto a plate processing machine such as, for example, a punch press and unloading the processed plate material from the plate processing machine is currently available in two types. One of the two types makes use of a single plate material conveyance unit which is capable of performing both of the loading of the unprocessed plate material and the unloading of the processed plate material such as disclosed in, for example, JP Laid-open Patent Publication No. 2007-326106, and the other of the two types makes use of a plate material loading unit (loader) dedicated solely for the loading and a processed plate material unloading unit (unloader) dedicated solely for the unloading such as disclosed in, for example, JP Laid-open Patent Publication No. H05-213482 and JP Laid-open Patent Publication No. 2004-237334. The latter has a higher plate material loading and unloading efficiency than that of the former since not only can the unloader undergo a loading setup of the unprocessed plate material while the loader performs a loading operation to load the unprocessed plate material, but also the loader can undergo a loading setup of the unprocessed plate material while the unloader undergoes an unloading operation.
Also, even though both types make use of the loader and the unloader, JP Laid-open Patent Publication No. H05-213482 discloses the structure in which the loader and the unloader travel along the same path, but JP Laid-open Patent Publication No. 2004-237334 discloses the structure in which the loader and the unloader travel along different paths. Where the loader and the unloader are configured so as to travel along the respective paths that are different from each other, the loader and the unloader do little to interfere in operation with each other, it is possible to minimize the loading standby time and the unloading standby time and, therefore, the efficiency of loading and unloading the plate material is further increased.
Also, since according to JP Laid-open Patent Publication No. 2004-237334 the path of travel of the loader and that of the unloader are disposed one above the other in a vertical direction, such an advantage can be appreciated that there is no need to secure a large space for installation of the loader and the unloader in a horizontal plane.
Plate materials to be supplied onto the plate processing machine are placed in a stacked fashion in an unprocessed plate material placement unit defined in the vicinity of the plate processing machine and, processed plate materials which have been successively processed by the plate processing machine are placed in a similarly stacked fashion in a processed plate material placement unit defined at a location different from the unprocessed plate material placement unit. Accordingly, in the plate material conveyance apparatus in which the path of travel of the loader and that of the unloader are disposed respectively at different vertical positions, there is a recognized need for a means for conveying horizontally the unprocessed plate material or the processed plate material between the unprocessed plate material placement unit and the processed plate material placement unit separate from the use of the loader and the unloader. For example, in the case where the unprocessed plate material placement unit is disposed immediately below the respective paths of travel of the loader and the unloader, the processed plate material after having been conveyed by the unloader is horizontally conveyed to the processed plate material placement unit that is disposed at a location distant from the path of travel referred to above.
In the case of the plate material conveyance apparatus disclosed in JP Laid-open Patent Publication No. 2004-237334, the horizontal conveyance of the plate material may be contemplated to implement with the use of a carriage. However, since the carriage is moved while a number of the processed plate materials are stacked on such carriage, the weight is high. Therefore, if such carriage is moved at a high speed, the stack of the processed plate materials on the carriage may be likely to become unstuck. For this reason, it is difficult for the carriage to be moved at such a high speed and, hence, a problem tends to arise that the cycle time in plate material loading and unloading may be extended correspondingly. Also, to move the carriage that is high in weight, a bulky driving source is required, resulting in the increase of electric power consumption.